The present invention relates to an eyeglass frame, a hinge for connecting a temple bar to an eyeglass frame, an eyeglass, and a method of manufacturing a hinge for linking a temple bar to an eyeglass frame. In particular the invention relates to eyeglass frames comprising hinges fitted with friction members.
As used herein the term eyeglass relates to the well known accessory which substantially comprises two lenses of glass or of other refractive or tinted, transparent material intended to be worn in front of the eyes of the user enabling him to obtain a corrected or a darkened view through the glasses, and a form of spectacle frame arranged to keep the lenses or glasses expediently fixed in the preferred position of use, where the user can look straight forward with both eyes and with parallel lines of sight through the respective lenses.
It is well known to provide such eyeglass frames with a frame front for holding the glasses and with a pair of temple bars for supporting the frame, which temple bars are connected to the frame front by means of hinges so as to allow the eyeglass to be folded up when not in use.
Even though a variety of eyeglasses are available, development is still taking place in order to find new solutions which might gain market shares, e.g. by offering particular features or cost benefits or through offering new aesthetic features.
U.S. Pat. No. Re 36 882 to Lindberg et al. discloses an eyeglass frame wherein the temple bar comprises a wire of which one end section has been wound into a coil for providing the exterior part of a hinge. The hinge pintle comprises a straight section of wire integral with the frame front. End sections of the pivot wire are angled laterally so as to provide double constraints for axial movement of the coil. This hinge design has proven successful, however, it is associated with some aestethical and functional limitations. Thus, in this hinge the laterally angled sections of pintle wire protrude beyond the coil which may be undesirable. Both hinge parts comprise metal and thus the hinge operation involves metal rubbing against metal, a combination which gives rise to wear. Thus, it is not practically possible to make this hinge with a predetermined level of friction.
Due to the pitch in the coil the turning of the hinge is bound to be linked with some axial displacement, thus giving rise to wear between the lateral end portions of the pintle wire and adjacent portions of the coil. This rubbing gives rise to friction, however, on reversing the direction of pivoting this frictions vanishes due to play between the lateral pintle wire sections followed by restablishment of some degree of friction against the opposite one of the lateral pintle wire sections. Most often friction to turning of the temples vanishes quickly leading to a not very attractive tactile feel of the parts tending to be loose.
WO 97/23803 discloses an eyeglass with hinge means comprising double concentric coils of wire. Thus, a wide coil basically integral with the frame provides a female thread engaged by the exterior of a narrower coil integral with temple bar. This solution relies on wire rubbing against wire and does not permit establishing and maintaining any predetermined level of friction in the hinge.
WO 00/29896 discloses a hinge comprising coils in respect of each of the temples and of the frame front, which coils have generally similar diameter and pitch in order that they may engage about a common pin with interengaging windings. In this solution metal rubs against metal on turning the pivot with the likely result that friction will vary over time.
WO 98/40778 discloses a hinge for an eyeglass with coils in respect of each of the temple bars and the frame front. The coils are mutually similar and engaged about a common pin, one coil on top of the other. The pin comprises an enlarged head to provide axial restraint. In this coil metal rubs on metal with the likely result that friction may vary over time. On turning of the temple bar, there is bound to be axial movement and separation among the parts according to the pitch of the coil. This implies that the head of the pin must allow axial play. This does not create an optimum tactile feel. Further, the head of the pin bears on the top most winding of one of the coils with the danger that the coil may work its way past the head by the screwing action.
WO 99/21046 discloses a hinge for an eyeglass comprising a strip of metal wrapped about pivot inserts of friction material. The resilient strap of metal applies a radially directed biasing force on the friction member so as to eliminate any play in the hinge and to establish a controlled level of friction. Only with respect to the axial constraint there is the danger of metal rubbing against metal, however, the axial forces are virtually nil due to the absence of coils or other factors that might create axial displacement. This hinge is not integrated with wire components.